//二分查找
class Solution {
    public int search(int[] nums, int target) {
        int left = 0;
        int right = nums.length-1;      
        while(left <= right){
            //int mid = (left +right)/2;//会溢出
            int mid = left + (right - left) / 2;//防止溢出
            if(nums[mid] > target){
                right = mid - 1;
            }else if(nums[mid] < target){
                left = mid +1;
            }else{
                return mid;
            }
        }
        return -1;
    }
}